For over 50 years, a major component of treatment for uterine cervical cancer (and sometimes uterine body cancer) has consisted of an internal radiation treatment known as brachytherapy. The types of brachytherapy are generally defined by the length of time that the tissue or organ is exposed to a therapeutic radiation source.
Low dose rate (LDR) treatments typically involve several days when the radioactive sources are temporarily placed in tissue. In some cases, permanent or semi-permanent implants may be positioned in the tissue for a much longer period of time.
In contrast, high dose rate (HDR) brachytherapy typically delivers a radiation dosage in a much higher rate than what is administered using LDR brachytherapy. The HDR brachytherapy procedures are therefore, shorter in duration and typically last just a few minutes. In addition to a much higher dose rate, the HDR brachytherapy provides for a precise delivery of the therapeutic radiation. Other advantages of the HDR brachytherapy include the ability to perform the HDR brachytherapy on outpatient basis and improved patient comfort and compliance.
In many HDR brachytherapy procedures, the placement of the radioactive material is automated. An automated HDR brachytherapy device is used to deliver a radioactive source precisely to the tissue or organ in need thereof. The automated HDR brachytherapy procedure is especially useful in the treatment of gynecologic cancers. Often, such treatment plans for HDR brachytherapy require a precise administration of the therapeutic radiation.
It is important that the therapeutic radiation be delivered to the target volume as precisely as possible. In such treatment plans, the clinician must select the optimum sized instrument, based on the individual patient's body configuration and the geometry of the target treatment area. It is especially important to administer a substantially homogeneous dose of radiation to the entire treatment volume, while preventing the irradiation of non-target areas of the patient's body. Thus, while HDR brachytherapy is widely used, the anatomical variations in the shape, thickness, orientation and size of the individual patients, provide challenges to the clinician to deliver a substantially uniform therapeutic radiation dosage.
Further, while HDR brachytherapy has become readily available, the instruments used have not changed substantially. One currently used instrument is a Fletcher-Suite type device that is composed of three components: one tandem and two culpostats or ovoids. The tandem is a narrow metallic cylinder that is introduced into the cervical canal through the vagina. The tip of the tandem is advanced up to the top of the uterine cavity. Part of the tandem exits the vagina to be accessed for source insertion. The two culpostats are cylinders that are attached to a rod-like device that also exits the vagina in a similar fashion to the tandem. The culpostats are inserted into the vagina and advanced to the very top of the vagina, one in the right lateral fornix just next to the external cervical canal and one to the left. These instruments are made of metal and rigid plastic. The culpostats are sized by placing caps over the basic metal culpostat. The largest size of placing caps that the patient can tolerate are inserted. A packing material is placed in the patient above and below the ends of the culpostat to physically displace the closest part of bladder and rectal mucosa away from the radiation source. Just a small movement of the instruments can reduce the radiation dose by as much as one third.
The Fletcher-Suite instrument is placed in surgery with the benefit of anesthesia. Women are admitted to the hospital after the insertion of this instrument, and radioactive sources are manually inserted into the applicator to deliver the radiation dose over 48 to 72 hours. These instruments cause great patient discomfort during the insertion thereof. Also, these instruments generally require the use of packing materials in order to move the bladder and rectum away from the instruments (and thus reduce their radiation exposure). These packing materials also caused great patient discomfort and often presented difficulties for the clinician during insertion thereof.
Thus, what is needed is an improved system to deliver intracavitary doses of radiation.